This investigation will compare the elastic, viscous, viscoelastic, and distortional components of the work of breathing in developing subjects with respiratory failure and in age- and size-matched controls, and relate this partition to breathing pattern and need for ventilatory support. Additionally, how the energy efficiency of the developing respiratory system is affected by alterations, produced by respiratory disease on breathing pattern, diaphragmatic configuration, and the uniformity of rib cage expansion will be analyzed.